Utilizing a portable magnetic resonance imaging (MRI) in the setting of an acute ischemic stroke in a patient with a cardiac implantable electronic device

Abstract

Background

Cardiac implantable electronic device (CIED) generally excludes patients from undergoing fixed, high-field magnetic resonance imaging (MRI). Acute ischemic stroke patients undergo MRI as a standard part of an assessment of infarct burden. The use of a portable MRI scanner may be useful in patients who have contraindications to high-field MRI. We present the first case of a patient with a CIED who required an endovascular thrombectomy (EVT) for large vessel occlusion. She underwent a low-field MRI in the operating room with the Hyperfine portable system.

Case

The patient is an 80-year-old female status post-CIED, on Eliquis who presented with an acute ischemic stroke. Her National Institutes of Health Stroke Scale (NIHSS) of 8. Imaging demonstrated a left M2 occlusion on computed tomography angiogram (CTA) of the head and neck. No lytics were used due to concomitant gastrointestinal bleed. While, admitted, her NIHSS increased to 15. A subsequent CTA demonstrated a left internal carotid artery terminus and M1 occlusion. She underwent EVT with thrombolysis in cerebral infarction (TICI) 3 revascularization. An MRI was performed intraoperatively using a Hyperfine system, which is a low-field, portable MRI, to assess infarct volume.

Conclusion

Hyperfine Swoop brain MRI may be safe for use in patients with contraindications to high-field MRI scans. Continued technological refinement will improve the quality of diffusion-weighted imaging. Larger studies will be required to generalize Hyperfine MRI-based imaging for patients with devices that exclude them from high-field imaging.

Introduction

Brain magnetic resonance imaging (MRI) is an integral part of acute ischemic stroke (AIS) evaluation to allow clinicians to assess infarct volume and help inform prognosis. ¹ Brain MRI does have limitations that include scan time, patient stability and transportation to the machine, claustrophobia, and body habitus. However, an increasing number of patients have implanted devices such as surgical hardware or cardiac implantable electronic device (CIED), which include pacemakers and cardioverter-defibrillators (implantable cardiac devices (ICDs)). ² The large majority of these devices are incompatible with performing MRI with traditional, high-field machines.

The Hyperfine Swoop portable MRI system is the world's first portable low-field MRI system approved by the Food and Drug Administration in 2020 to evaluate brain tissue. It can perform T1, T2, Fluid Attenuated Inversion Recovery (FLAIR), and diffusion-weighted imaging sequences in <30 min. Unlike traditional 1.5 Tesla MRI machines, its magnetic field is only 0.064 Tesla. As such, this system may be an option to scan patients who have hardware that is incompatible with high-field MRI. Additionally, as a bedside device, it is more accessible and can be utilized in virtually any location. Its portability is especially compelling in an emergency setting when compared to a traditional MRI. Hence, the use of this technology may especially be useful for rapid diagnosis and management in AIS patients.

We report the first case of a patient with a CIED who underwent endovascular thrombectomy (EVT) for a large vessel occlusion stroke. She underwent an MRI in the operating room with the Hyperfine Swoop system. This system allowed us to obtain imaging of the brain tissue after thrombectomy in a patient who would otherwise be unable to undergo an MRI.

Case

The patient is an 80-year-old female with a past medical history of congestive heart failure, hypertension, atrial fibrillation, status post ICD on Eliquis, aortic stenosis status post transcatheter aortic valve replacement in October 2022, hypothyroidism, hyperlipidemia, and depression who was admitted at an outside hospital for a congestive heart failure exacerbation and low hemoglobin due to a gastrointestinal (GI) bleed. Four days into her admission she developed aphasia, right-sided facial droop, and confusion with a National Institutes of Health Stroke Scale (NIHSS) of 8. Imaging was significant for a left M2 occlusion on computed tomography angiogram (CTA) of the brain and neck.

She was transferred to our hospital and had an NIHSS of 3 and a modified Rankin Score (mRS) of 0 without any intervention. A computed tomography brain perfusion showed a decreased perfusion mismatch of 4 mL in the left middle cerebral artery territory and a CTA revealed moderate stenosis of the left internal carotid artery (ICA). No lytics were used due to her active GI bleed requiring packed red blood cell transfusion, and she did not receive a thrombectomy due to her imaging and exam findings.

During her stay, she developed symptoms concerning left-sided stenosis, with an NIHSS of 15, and a CTA demonstrating an ICA terminus and left M1 occlusion (Figure 1). A decision was made to undergo EVT from a carotid cutdown as gaining access from her femoral and radial artery was unsuccessful. The procedure was successful, and she achieved thrombolysis in cerebral infarction 3 revascularization (Figure 2). The Hyperfine Swoop MRI was performed in the operating room immediately following EVT to assess infarct volume (Figure 3).

Figure 1.

Pre-operative anterior–posterior (a) and lateral (b) views of a cerebral angiogram demonstrating a left M1 occlusion.

Figure 2.

Post-operative anterior–posterior (a) and lateral (b) views of a cerebral angiogram demonstrating a TICI 3 revascularized MCA.

TICI: thrombolysis in cerebral infarction; MCA: middle cerebral artery.

Figure 3.

Post-operative T2 (a), FLAIR (b), and diffusion-restricted sequences (c) of MRI taken by the Hyperfine Swoop system. There is no sign of diffusion restriction or ischemia on the scans.

FLAIR: Fluid Attenuated Inversion Recovery; MRI: magnetic resonance imaging.

The patient recovered well neurologically and returned to an NIHSS of 2. Chronically, the patient's respiratory predisposed her to pneumonia, ultimately leading to her passing prior to her 90-day mRS follow-up. Informed consent was obtained from her family.

Discussion

We report a case where a patient was able to receive a brain MRI despite having an ICD by utilizing a low-field portable bedside MRI. The imaging obtained allowed us to assess her infarct volume. We demonstrated that the Hyperfine Swoop system may also be used to capture brain tissue images in case of emergency care. Previous studies have demonstrated the efficacy of portable MRI in resecting a suprasellar mass, but our case marks the first use of portable MRI systems in an emergent setting, which could represent a model of more accessible care in the future. ³

Given the fact that the population of the United States continues to age, combined with the fact that CIEDs are much more prevalent in older patients, these devices will continue to be an issue for patients who need brain imaging. Furthermore, ischemic strokes are more common in older patients with incidence increasing each year, so obtaining brain MRIs in this subset of patients will also be a challenge as part of their evaluation and treatment. ⁴ Finally, access to brain tissue imaging is not only important in post-stroke assessment, but also as a part of a broader assessment of the brain beyond AIS, such as inflammatory, infectious, and degenerative diseases in patients who have contraindications to high-field MRI.

The Hyperfine Swoop system is cost-effective compared to the traditional 1.5 Tesla MRI. With the benefits that low-field portable MRI systems offer coupled with their lower cost, they may be efficient systems to utilize in surgical, post-surgical, and outpatient settings.^3,5,6

Conclusion

Hyperfine Swoop beside brain MRI may be safe for use in patients with implantable devices such as CIED, especially in settings that require high-quality images for immediate diagnosis or management such as AIS. Moreover, it further represents an alternative method for obtaining brain MRIs in patients in whom high-field brain MRIs are not an option. Further studies need to be performed to discuss the safety of its usage in patients with CIEDs and compare the accuracy and image quality with traditional high-field MRI machines.